Fuel cells, which are capable of generating electric power with high efficiency even when they are configured as small-sized devices, have been developed as power generators of distributed energy sources. However, there is no general infrastructure to supply hydrogen gas which is used by a fuel cell when the fuel cell generates electric power. Therefore, in a case where a fuel cell is utilized as a distributed power generator, it is often the case that the fuel cell is installed together with a hydrogen generator. The hydrogen generator is configured to cause a steam reforming reaction of a raw material such as city gas or LPG obtained from an existing fossil fuel infrastructure, thereby generating a hydrogen-containing gas.
One of the advantages of distributed energy sources is to make it possible to obtain necessary energy when necessary. It is desirable for such a distributed energy source to stop operating when there is no energy demand, and it is necessary for the distributed energy source to be capable of frequent start-ups and stops.
In a re-starting operation or pressure compensation operation performed after the hydrogen generator has stopped operating, the raw material is supplied to the hydrogen generator at a suitable timing in such a predetermined temperature range as not to cause thermal decomposition of the raw material in the hydrogen generator (see Patent Literature 1, for example). Accordingly, in the hydrogen generator, carbon deposition onto a reforming catalyst is suppressed, which reduces damage to the catalyst such as cracks.
Odorants such as mercaptans, sulfides, or thiophenes are added to the raw material to be supplied to the hydrogen generator. The raw material is, for example, city gas or LPG obtained from an existing fossil fuel infrastructure. These sulfur compounds poison the reforming catalyst, thereby degrading the function of the reforming catalyst. Therefore, it is necessary to remove such sulfur compounds from the raw material before sending the raw material to the reforming catalyst. One proposed method for removing sulfur compounds from the raw material is a hydrodesulfurization method of desulfurizing sulfur components by using the hydrogen-containing gas generated by the hydrogen generator (see Patent Literatures 2 and 3, for example).